Hot pressed PEEK/Graphite thin film laminate composites: Thermal properties and mechanical behavior

Abstract

This work studies high-performance laminate composite materials made of graphite and poly(ether-ether-ketone) (PEEK). The composites were fabricated using a hot press method at a temperature below 310°C, and their structural, thermal, and mechanical properties were evaluated and discussed. SEM images of the laminate cross-section indicated a solid interfacial interaction between PEEK and graphite due to the high joining load. Thermogravimetric analysis (TGA) results showed that 3-layered PEEK/graphite/PEEK (PGP) and 5-layered PEEK/graphite/PEEK/graphite/PEEK (PG)2P composites had better thermal stability at high temperatures compared to neat PEEK. The mechanical properties tests showed that PGP had a higher Ultimate Tensile Strength (UTS) by 52% compared to neat graphite. However, adding another layer of graphite (PG)2P caused a decrease in UTS by 9.6% due to the higher volume fraction of graphite. The nanoindentation tests confirmed these findings: Young's modulus increased from 1.64 to 2.58 GPa, and the hardness increased from 0.164 to 0.178 GPa for PGP and (PG)2P, respectively. Additionally, XRD analysis indicated that the crystallinity of fabricated composites increased by 35.5% compared with pristine PEEK. The present study confirms that using PEEK and graphite sheets in composite fabrication through hot pressing improves thermal and mechanical properties.